1. Field of the Invention
This invention relates generally to surgical instruments for improving the outcome of percutaneous transluminal coronary angioplasty procedures, and more particularly to a light delivery system incorporating a means for irradiating a treatment site with radiant energy, e.g., U.V. or visible light, while simultaneously flushing the blood from the light path. It has been previously found that radiating the treatment site reduces the incidences of restenosis.
2. Discussion of the Prior Art
U.S. patent application Ser. No. 08/425,858, filed Apr. 20, 1995, and entitled "Method and Apparatus for Treating Vascular Tissue Following Angioplasty to Minimize Restenosis", which is assigned to applicant's assignee, provides a discussion of the prior art relating to known methods and apparatus for reducing the proliferation of smooth muscle cells at the site of a stenotic lesion that had earlier been subjected to balloon angioplasty by exposure of the treatment site to U.V. light. The system described and claimed in the above-referenced pending patent application constitutes an improvement over the prior art, especially in the manner in which the involved tissue is irradiated with U.V. light in a controlled fashion by a step-wise displacement of a radiant energy-emitting fiber. The disclosure contained in the aforereferenced application Ser. No. 08/425,858 is hereby incorporated by reference in the present application as if fully set forth herein.
In efforts to irradiate endothelial and intimal tissue with light following an angioplasty procedure, a difficulty has arisen in delivering light of low wavelength at an adequate intensity to the treatment site due to the presence of blood or other light absorbing substances between the light energy emitter and the tissue to be treated. While the apparatus disclosed in the aforereferenced pending patent application of applicant's assignee is effective in clearing the site of most blood due to the expansion of a balloon member against the wall of the vessel being treated, even the thin remaining layer of blood or blood contaminated saline trapped between the exterior of the balloon and the blood vessel drastically reduces the transmissivity of U.V. light at the desired wavelength. It has been found that even a 1% concentration of blood in saline can reduce the transmissivity of U.V. light at a wavelength of 257 nm by 70% or more. Thus, a need exists for an improved system for irradiating the interior lining of a blood vessel to impart to the system the ability to expose the blood vessel tissue to radiant energy at a sufficiently high, efficacious intensity.